The function performed by mixing heads of this kind is to mix chemical components, for example, a polyol and an isocyanate, with one another for reaction in a mixing chamber and directly to introduce the mixture thus formed into a receiving vessel, preferably into a mold cavity.
Various attempts have already been made to remove from the mixing chamber any residues of the components or of the mixture which adhere to it. In cases where the mixing head is combined with molds, it is now common practice to remove the sprue and the residue left in the mixing chamber from the mold together with the finished molding in order to eliminate the need to flush out the mixing chamber. In the case of slide-type mixing heads, however, it has been found that, on completion of mixing, i.e. when the slide is returned from the mixing position to the rest position, the tail ends of the jets of components issuing from the injection openings cannot be mixed with one another, with the result that they remain adhering to the walls of the mixing chamber without having reacted. The liquid component residues first become tacky and then harden to form a solid, fully reacted mixture residue. Some of the liquid and tacky parts remain adhering to, and foul the walls of the mixing chamber. As a result, the mixing chamber becomes increasingly covered with deposits during operation and has to be cleaned at fairly frequent intervals.
An object of the present invention is to provide a mixing head in which deposits of this kind are prevented from forming.